Add vim headers to Dockerfile

Sometimes I have to use nano to get the tabs right because it is different than my local
settings. Remove the tab pain from some users. @tianon don't kill me, wanted to see if 
I could get away with this. If so, I could do them all... (shell scripts)? Or should we just forget it?

```vim
syntax on
filetype plugin indent on
set list listchars=tab:»·,nbsp:_,extends:¬
set noet ts=4 sw=4
```